Oxide etch selectivity enhancement

ABSTRACT

A method of etching exposed silicon oxide on patterned heterogeneous structures is described and includes a gas phase etch using plasma effluents formed in a remote plasma. The remote plasma excites a fluorine-containing precursor in combination with an oxygen-containing precursor. Plasma effluents within the remote plasma are flowed into a substrate processing region where the plasma effluents combine with water vapor or an alcohol. The combination react with the patterned heterogeneous structures to remove an exposed silicon oxide portion faster than an exposed silicon nitride portion. The inclusion of the oxygen-containing precursor may suppress the silicon nitride etch rate and result in unprecedented silicon oxide etch selectivity.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of U.S. Prov. Pat. App. No.62/055,587 filed Sep. 25, 2014, and titled “R3X WITH O2 ADDITION” byChen et al., which is hereby incorporated herein in its entirety byreference for all purposes.

FIELD

Embodiments of the invention relate to selectively etching siliconoxide.

BACKGROUND

Integrated circuits are made possible by processes which produceintricately patterned material layers on substrate surfaces. Producingpatterned material on a substrate requires controlled methods forremoval of exposed material. Chemical etching is used for a variety ofpurposes including transferring a pattern in photoresist into underlyinglayers, thinning layers or thinning lateral dimensions of featuresalready present on the surface. Often it is desirable to have an etchprocess which etches one material faster than another helping e.g. apattern transfer process proceed. Such an etch process is said to beselective of the first material relative to the second material. As aresult of the diversity of materials, circuits and processes, etchprocesses have been developed with a selectivity towards a variety ofmaterials.

Dry etch processes are often desirable for selectively removing materialfrom semiconductor substrates. The desirability stems from the abilityto gently remove material from miniature structures with minimalphysical disturbance. Dry etch processes also allow the etch rate to beabruptly stopped by removing the gas phase reagents. Some dry-etchprocesses involve the exposure of a substrate to remote plasmaby-products formed from one or more precursors. For example, remoteplasma excitation of ammonia and nitrogen trifluoride enables siliconoxide to be selectively removed from a patterned substrate when theplasma effluents are flowed into the substrate processing region.

Methods are needed to progressively expand this suite of selectivitiesin order to enable novel process flows.

SUMMARY

A method of etching exposed silicon oxide on patterned heterogeneousstructures is described and includes a gas phase etch using plasmaeffluents formed in a remote plasma. The remote plasma excites afluorine-containing precursor in combination with an oxygen-containingprecursor. Plasma effluents within the remote plasma are flowed into asubstrate processing region where the plasma effluents combine withwater vapor or an alcohol. The combination react with the patternedheterogeneous structures to remove an exposed silicon oxide portionfaster than an exposed silicon nitride portion. The inclusion of theoxygen-containing precursor may suppress the silicon nitride etch rateand result in unprecedented silicon oxide etch selectivity.

Embodiments of the invention include methods of etching a patternedsubstrate. The methods include placing the patterned substrate in asubstrate processing region of a substrate processing chamber. Thepatterned substrate has an exposed silicon oxide portion and an exposedsilicon nitride portion. The methods further include flowing aradical-fluorine precursor into the substrate processing region. Themethods further include flowing a radical-oxygen precursor into thesubstrate processing region. The methods further include flowing ahydrogen-and-oxygen-containing precursor into the substrate processingregion without first passing the hydrogen-and-oxygen-containingprecursor through any plasma. The hydrogen-and-oxygen-containingprecursor comprises an OH group. The methods further include etching theexposed silicon oxide portion. The exposed silicon oxide portion etchesat a first etch rate and the second exposed silicon oxide portion etchesat a second etch rate which is lower than the first etch rate.

Embodiments of the invention include methods of etching a patternedsubstrate. The methods include placing the patterned substrate in asubstrate processing region of a substrate processing chamber. Thepatterned substrate includes an exposed silicon oxide portion and anexposed silicon nitride portion. The methods further include flowing afluorine-containing precursor and an oxygen-containing precursor into aremote plasma region fluidly coupled to the substrate processing regionwhile forming a remote plasma in the remote plasma region to produceplasma effluents. The methods further include flowing ahydrogen-and-oxygen-containing precursor into the substrate processingregion without first passing the hydrogen-and-oxygen-containingprecursor through the remote plasma region. Thehydrogen-and-oxygen-containing precursor comprises an O—H bond. Themethods further include etching the exposed silicon oxide portion byflowing the plasma effluents into the substrate processing region. Theexposed silicon oxide portion etches at a first etch rate and theexposed silicon nitride portion etches at a second etch rate which islower than the first etch rate.

Embodiments of the invention include methods of etching a patternedsubstrate. The methods include placing the patterned substrate in asubstrate processing region of a substrate processing chamber. Thepatterned substrate has an exposed silicon oxide portion and an exposedsilicon nitride portion. The methods further include flowing nitrogentrifluoride and molecular oxygen into a remote plasma region fluidlycoupled to the substrate processing region while forming a remote plasmain the remote plasma region to produce plasma effluents. The methodsfurther include combining the plasma effluents with water vapor in thesubstrate processing region. The methods further include etching theexposed silicon oxide portion with the combination of the plasmaeffluents and the water vapor. The exposed silicon oxide portion etchesat a first etch rate and the exposed silicon nitride portion etches at asecond etch rate which is lower than the first etch rate.

Additional embodiments and features are set forth in part in thedescription that follows, and in part will become apparent to thoseskilled in the art upon examination of the specification or may belearned by the practice of the disclosed embodiments. The features andadvantages of the disclosed embodiments may be realized and attained bymeans of the instrumentalities, combinations, and methods described inthe specification.

DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the embodimentsmay be realized by reference to the remaining portions of thespecification and the drawings.

FIG. 1 is a flow chart of a silicon oxide selective etch processaccording to embodiments.

FIG. 2 is a plot of silicon nitride etch loss according to embodiments.

FIG. 3A shows a schematic cross-sectional view of a substrate processingchamber according to embodiments.

FIG. 3B shows a schematic cross-sectional view of a portion of asubstrate processing chamber according to embodiments.

FIG. 3C shows a bottom view of a showerhead according to embodiments.

FIG. 4 shows a top view of an exemplary substrate processing systemaccording to embodiments.

In the appended figures, similar components and/or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If only the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

DETAILED DESCRIPTION

A method of etching exposed silicon oxide on patterned heterogeneousstructures is described and includes a gas phase etch using plasmaeffluents formed in a remote plasma. The remote plasma excites afluorine-containing precursor in combination with an oxygen-containingprecursor. Plasma effluents within the remote plasma are flowed into asubstrate processing region where the plasma effluents combine withwater vapor or an alcohol. The combination react with the patternedheterogeneous structures to remove an exposed silicon oxide portionfaster than an exposed silicon nitride portion. The inclusion of theoxygen-containing precursor may suppress the silicon nitride etch rateand result in unprecedented silicon oxide etch selectivity.

Selective remote gas phase etch processes have used ahydrogen-containing precursor of ammonia (NH₃) and a fluorine-containingprecursor of nitrogen trifluoride (NF₃) which together flow through aremote plasma and into a substrate processing region. Alternative remotegas phase etch processes have also been developed which do not requireammonia. These remote gas phase etch processes remove oxide films muchmore rapidly than, e.g. silicon. However, even with the alternativeprocesses, there is still a non-negligible loss of silicon nitride whichis becoming a problem as linewidths decrease toward and below tennanometers. The methods disclosed herein may exhibit a significantlygreater etch rate selectivity of silicon oxide (regardless of dopants ordeposition method) relative to silicon nitride.

In order to better understand and appreciate the invention, reference isnow made to FIG. 1 which is a flow chart of a silicon oxide selectiveetch process 101 according to embodiments. Prior to the first operation,the substrate is patterned and an exposed silicon oxide portion isformed on the patterned substrate. An exposed silicon nitride portion isalso formed on the patterned substrate. The patterned substrate is thenplaced within the substrate processing region in operation 110.

Nitrogen trifluoride and molecular oxygen (O₂) are flowed into a remoteplasma region (operation 120). The nitrogen trifluoride and oxygen arecollectively excited in a remote plasma formed in the remote plasmaregion. The remote plasma system is positioned next to the substrateprocessing region and fluidly coupled through a showerhead. The remoteplasma region may be within a distinct module from the processingchamber and/or a compartment within the processing chamber. The plasmaeffluents formed in the remote plasma are then flowed into the substrateprocessing region (operation 130). Water vapor is simultaneously flowedinto the substrate processing region and combined with the plasmaeffluents. The water vapor is not passed through the remote plasmaregion and therefore may only be excited by interaction with the plasmaeffluents according to embodiments. The water vapor is not passedthrough any remote plasma region before entering the substrateprocessing region in embodiments.

Other sources of fluorine may be used to augment or replace the nitrogentrifluoride. In general, a fluorine-containing precursor is flowed intothe plasma region and the fluorine-containing precursor comprises atleast one precursor selected from the group consisting of atomicfluorine, diatomic fluorine, nitrogen trifluoride, carbon tetrafluoride,hydrogen fluoride and xenon difluoride in embodiments. Other sources ofoxygen may be used to augment or replace the nitrogen trifluoride. Ingeneral, an oxygen-containing precursor is flowed into the plasma regionand the fluorine-containing precursor comprises at least one precursorselected from the group consisting of molecular oxygen (O₂), ozone (O₃),dinitrogen oxide (N₂O), hyponitrite (N₂O₂) or nitrogen dioxide (NO₂) inembodiments.

The patterned substrate is selectively etched (operation 140) such thatthe exposed silicon oxide is removed at a higher rate than the exposedsilicon nitride. The reactive chemical species are removed and thesubstrate is removed from the substrate processing region (operation150).

Reference is now made to FIG. 2 which is a plot of silicon nitride etchloss during silicon oxide etch processes including etch process 101according to embodiments. The addition of the oxygen-containingprecursor reduces the etch loss of silicon nitride regardless of whetherthe nitrogen trifluoride is flowed with a high flow rate (210), mediumflow rate (220) or low flow rate (210). The low flow rate curvecorresponds with a nitrogen trifluoride flow rate of 5 sccm. The mediumflow rate and high flow rate curves correspond with 15 sccm and 25 sccm,respectively. At a low NF₃ flow rate of 5 sccm, the loss of siliconnitride is highest of all three flow rates when no oxygen-containingprecursor is included in the remote plasma region. Low NF3 flow ratesare desirable for many applications to increase selectivity amongstdifferent quality silicon oxide portions. As oxygen-containing precursoris introduced and its flow rate increased, the silicon nitride etch lossplummets in the case of the low nitrogen trifluoride flow rate such thatthe etch loss even drops below the medium and high flow rates. Combiningthe low flow rate of nitrogen trifluoride with a moderate flow ofoxygen-containing precursor results in an unprecedented silicon oxideetch selectivity relative to silicon nitride.

The methods presented herein exhibit high etch selectivity of theexposed silicon oxide portion relative to an exposed silicon nitrideportion. In operation 140, the etch selectivity of the exposed siliconoxide portion relative to the exposed silicon nitride portion may begreater than 80:1, greater than 120:1 or greater than 150:1 according toembodiments. The etch rate of the exposed silicon oxide portion may bereferred to as the first etch rate and the etch rate of the siliconnitride portion may be referred to herein as the second etch rate. Thefirst etch rate may exceed the second etch rate by a factor of more than80, more than 120 or more than 150 in embodiments. The observedselectivity (silicon oxide relative to silicon nitride) depends on thedeposition technique, quality and dopant levels in the silicon oxide. Inone example the selectivity was observed to increase from 130 to 220using the techniques presented herein for low quality sacrificialsilicon oxide. Thus, the first etch rate may exceed the second etch rateby a factor of more than 150, more than 175 or more than 200 in someembodiments.

Cycling has been found to further increase the observed etchselectivities of silicon oxide relative to silicon nitride. Therefore,the unused reactants and other process effluents may be removed from thesubstrate processing region after operation 140 and before operation150. Following process effluent removal, operations 120-140 oroperations 130-140 may be repeated to remove additional silicon oxidefrom the exposed silicon oxide portion.

The gas phase etches described herein may not produce solid residue evenat low substrate temperatures. Elimination of solid residue during theprocess avoids any potential disturbance of delicate features such asthin line structures. Elimination of solid residue also simplifies theprocess flows and decreases processing costs by removing a sublimationstep. The fluorine-containing precursor, the remote plasma region and/orthe oxygen-containing precursor are devoid of hydrogen during operation140 in embodiments. The plasma effluents may also be devoid of hydrogenaccording to embodiments. Lack of hydrogen in the remote plasma regionensures minimal or no production of solid by-products on the patternedsubstrate.

In the examples presented herein, water was introduced through theshowerhead into the substrate processing region without prior plasmaexcitation. Generally speaking, a hydrogen-and-oxygen-containingprecursor may be introduced in place of or to augment the moisture. Thehydrogen-and-oxygen-containing precursor may include an OH group inembodiments. The hydrogen-and-oxygen-containing precursor may be one ofwater or an alcohol according to embodiments. The alcohol may includeone or more of methanol, ethanol and isopropyl alcohol in embodiments.The hydrogen-and-oxygen-containing-precursor may not pass through aremote plasma before entering the substrate processing region accordingto embodiments.

The pressure in the substrate processing region and the remote plasmaregion(s) during the etching operations may be between 0.1 Torr and 50Torr, between 1 Torr and 15 Torr or between 5 Torr and 10 Torr inembodiments. The temperature of the patterned substrate during theetching operations may be between −20° C. and 250° C., between 0° C. and50° C. or between 5° C. and 20° C. in embodiments. Flow rate ranges aregiven in the course of describing exemplary equipment.

The method also includes applying power to the fluorine-containingprecursor and the oxygen-containing precursor during operation 120 inthe remote plasma regions to generate the plasma effluents. The plasmaparameters described herein apply to remote plasmas used to etch thepatterned substrate. As would be appreciated by one of ordinary skill inthe art, the plasma may include a number of charged and neutral speciesincluding radicals and ions. The plasma may be generated using knowntechniques (e.g., RF, capacitively coupled, inductively coupled). In anembodiment, the remote plasma power may be applied to the remote plasmaregion at a level between 500 W and 10 kW for a remote plasma externalto the substrate processing chamber. The remote plasma power may beapplied using inductive coils, in embodiments, in which case the remoteplasma will be referred to as an inductively-coupled plasma (ICP) or maybe applied using capacitive plates, in which case the remote plasma willbe referred to as a capacitive-coupled plasma (CCP). According toembodiments, the remote plasma power may be applied to the remote plasmaregion at a level between 25 watts and 500 watts for a remote plasmawithin the substrate processing chamber. Other possible plasmaparameters and ranges will be described along with exemplary equipmentherein.

For both treatment remote plasmas and etch remote plasmas, the flows ofthe precursors into the remote plasma region may further include one ormore relatively inert gases such as He, N₂, Ar. The inert gas can beused to improve plasma stability, ease plasma initiation, and improveprocess uniformity. Argon may be helpful, as an additive, to promote theformation of a stable plasma. Process uniformity is generally increasedwhen helium is included. These additives are present in embodimentsthroughout this specification. Flow rates and ratios of the differentgases may be used to control etch rates and etch selectivity.

In embodiments, an ion suppressor (which may be the showerhead) may beused to provide radical and/or neutral species for gas-phase etching.The ion suppressor may also be referred to as an ion suppressionelement. In embodiments, for example, the ion suppressor is used tofilter etching plasma effluents en route from the remote plasma regionto the substrate processing region. The ion suppressor may be used toprovide a reactive gas having a higher concentration of radicals thanions. Plasma effluents pass through the ion suppressor disposed betweenthe remote plasma region and the substrate processing region. The ionsuppressor functions to dramatically reduce or substantially eliminateionic species traveling from the plasma generation region to thesubstrate. The ion suppressors described herein are simply one way toachieve a low electron temperature in the substrate processing regionduring the gas-phase etch processes described herein.

In embodiments, an electron beam is passed through the substrateprocessing region in a plane parallel to the substrate to reduce theelectron temperature of the plasma effluents. A simpler showerhead maybe used if an electron beam is applied in this manner. The electron beammay be passed as a laminar sheet disposed above the substrate inembodiments. The electron beam provides a source of neutralizingnegative charge and provides a more active means for reducing the flowof positively charged ions towards the substrate and increasing the etchselectivity in embodiments. The flow of plasma effluents and variousparameters governing the operation of the electron beam may be adjustedto lower the electron temperature measured in the substrate processingregion.

The electron temperature may be measured using a Langmuir probe in thesubstrate processing region during excitation of a plasma in the remoteplasma. In aluminum removal embodiments, the electron temperature may beless than 0.5 eV, less than 0.45 eV, less than 0.4 eV, or less than 0.35eV. These extremely low values for the electron temperature are enabledby the presence of the electron beam, showerhead and/or the ionsuppressor. Uncharged neutral and radical species may pass through theelectron beam and/or the openings in the ion suppressor to react at thesubstrate. Such a process using radicals and other neutral species canreduce plasma damage compared to conventional plasma etch processes thatinclude sputtering and bombardment. Embodiments of the present inventionare also advantageous over conventional wet etch processes where surfacetension of liquids can cause bending and peeling of small features. Inpoint of contrast, the electron temperature during the aluminum oxideremoval process may be greater than 0.5 eV, greater than 0.6 eV orgreater than 0.7 eV according to embodiments.

The substrate processing region may be described herein as “plasma-free”during the etch processes described herein. “Plasma-free” does notnecessarily mean the region is devoid of plasma. Ionized species andfree electrons created within the plasma region may travel through pores(apertures) in the partition (showerhead) at exceedingly smallconcentrations. The borders of the plasma in the chamber plasma regionmay encroach to some small degree upon the substrate processing regionthrough the apertures in the showerhead. Furthermore, a low intensityplasma may be created in the substrate processing region withouteliminating desirable features of the etch processes described herein.All causes for a plasma having much lower intensity ion density than thechamber plasma region during the creation of the excited plasmaeffluents do not deviate from the scope of “plasma-free” as used herein.

FIG. 3A shows a cross-sectional view of an exemplary substrateprocessing chamber 1001 with a partitioned plasma generation regionwithin the processing chamber. During film etching, a process gas may beflowed into chamber plasma region 1015 through a gas inlet assembly1005. A remote plasma system (RPS) 1002 may optionally be included inthe system, and may process a first gas which then travels through gasinlet assembly 1005. The process gas may be excited within RPS 1002prior to entering chamber plasma region 1015. Accordingly, thefluorine-containing precursor as discussed above, for example, may passthrough RPS 1002 or bypass the RPS unit in embodiments.

A cooling plate 1003, faceplate 1017, ion suppressor 1023, showerhead1025, and a substrate support 1065 (also known as a pedestal), having asubstrate 1055 disposed thereon, are shown and may each be includedaccording to embodiments. Pedestal 1065 may have a heat exchange channelthrough which a heat exchange fluid flows to control the temperature ofthe substrate. This configuration may allow the substrate 1055temperature to be cooled or heated to maintain relatively lowtemperatures, such as between −20° C. to 200° C. Pedestal 1065 may alsobe resistively heated to relatively high temperatures, such as between100° C. and 1100° C., using an embedded heater element.

Exemplary configurations may include having the gas inlet assembly 1005open into a gas supply region 1058 partitioned from the chamber plasmaregion 1015 by faceplate 1017 so that the gases/species flow through theholes in the faceplate 1017 into the chamber plasma region 1015.Structural and operational features may be selected to preventsignificant backflow of plasma from the chamber plasma region 1015 backinto the supply region 1058, gas inlet assembly 1005, and fluid supplysystem 1010. The structural features may include the selection ofdimensions and cross-sectional geometries of the apertures in faceplate1017 to deactivate back-streaming plasma. The operational features mayinclude maintaining a pressure difference between the gas supply region1058 and chamber plasma region 1015 that maintains a unidirectional flowof plasma through the showerhead 1025. The faceplate 1017, or aconductive top portion of the chamber, and showerhead 1025 are shownwith an insulating ring 1020 located between the features, which allowsan AC potential to be applied to the faceplate 1017 relative toshowerhead 1025 and/or ion suppressor 1023. The insulating ring 1020 maybe positioned between the faceplate 1017 and the showerhead 1025 and/orion suppressor 1023 enabling a capacitively coupled plasma (CCP) to beformed in the chamber plasma region.

The plurality of holes in the ion suppressor 1023 may be configured tocontrol the passage of the activated gas, i.e., the ionic, radical,and/or neutral species, through the ion suppressor 1023. For example,the aspect ratio of the holes, or the hole diameter to length, and/orthe geometry of the holes may be controlled so that the flow ofionically-charged species in the activated gas passing through the ionsuppressor 1023 is reduced. The holes in the ion suppressor 1023 mayinclude a tapered portion that faces chamber plasma region 1015, and acylindrical portion that faces the showerhead 1025. The cylindricalportion may be shaped and dimensioned to control the flow of ionicspecies passing to the showerhead 1025. An adjustable electrical biasmay also be applied to the ion suppressor 1023 as an additional means tocontrol the flow of ionic species through the suppressor. The ionsuppression element 1023 may function to reduce or eliminate the amountof ionically charged species traveling from the plasma generation regionto the substrate. Uncharged neutral and radical species may still passthrough the openings in the ion suppressor to react with the substrate.

Plasma power can be of a variety of frequencies or a combination ofmultiple frequencies. In the exemplary processing system the plasma maybe provided by RF power delivered to faceplate 1017 relative to ionsuppressor 1023 and/or showerhead 1025. The RF power may be betweenabout 10 watts and about 5000 watts, between about 100 watts and about2000 watts, between about 200 watts and about 1500 watts, or betweenabout 200 watts and about 1000 watts in embodiments. The RF frequencyapplied in the exemplary processing system may be low RF frequenciesless than about 200 kHz, high RF frequencies between about 10 MHz andabout 15 MHz, or microwave frequencies greater than or about 1 GHz inembodiments. The plasma power may be capacitively-coupled (CCP) orinductively-coupled (ICP) into the remote plasma region.

A precursor, for example a fluorine-containing precursor and anoxygen-containing precursor, may be flowed into substrate processingregion 1033 by embodiments of the showerhead described herein. Excitedspecies derived from the process gas in chamber plasma region 1015 maytravel through apertures in the ion suppressor 1023, and/or showerhead1025 and react with an additional precursor flowing into substrateprocessing region 1033 from a separate portion of the showerhead.Alternatively, if all precursor species are being excited in chamberplasma region 1015, no additional precursors may be flowed through theseparate portion of the showerhead. Little or no plasma may be presentin substrate processing region 1033 during the remote plasma etchprocess. Excited derivatives of the precursors may combine in the regionabove the substrate and/or on the substrate to etch structures or removespecies from the substrate.

The processing gases may be excited in chamber plasma region 1015 andmay be passed through the showerhead 1025 to substrate processing region1033 in the excited state. While a plasma may be generated in substrateprocessing region 1033, a plasma may alternatively not be generated inthe processing region. In one example, the only excitation of theprocessing gas or precursors may be from exciting the processing gasesin chamber plasma region 1015 to react with one another in substrateprocessing region 1033. As previously discussed, this may be to protectthe structures patterned on substrate 1055.

FIG. 3B shows a detailed view of the features affecting the processinggas distribution through faceplate 1017. The gas distribution assembliessuch as showerhead 1025 for use in the processing chamber section 1001may be referred to as dual channel showerheads (DCSH) and areadditionally detailed in the embodiments described in FIG. 3A as well asFIG. 3C herein. The dual channel showerhead may provide for etchingprocesses that allow for separation of etchants outside of theprocessing region 1033 to provide limited interaction with chambercomponents and each other prior to being delivered into the processingregion.

The showerhead 1025 may comprise an upper plate 1014 and a lower plate1016. The plates may be coupled with one another to define a volume 1018between the plates. The coupling of the plates may be so as to providefirst fluid channels 1019 through the upper and lower plates, and secondfluid channels 1021 through the lower plate 1016. The formed channelsmay be configured to provide fluid access from the volume 1018 throughthe lower plate 1016 via second fluid channels 1021 alone, and the firstfluid channels 1019 may be fluidly isolated from the volume 1018 betweenthe plates and the second fluid channels 1021. The volume 1018 may befluidly accessible through a side of the gas distribution assembly 1025.Although the exemplary system of FIGS. 3A-3C includes a dual-channelshowerhead, it is understood that alternative distribution assembliesmay be utilized that maintain first and second precursors fluidlyisolated prior to substrate processing region 1033. For example, aperforated plate and tubes underneath the plate may be utilized,although other configurations may operate with reduced efficiency or notprovide as uniform processing as the dual-channel showerhead described.

In the embodiment shown, showerhead 1025 may distribute via first fluidchannels 1019 process gases which contain plasma effluents uponexcitation by a plasma in chamber plasma region 1015. In embodiments,the process gas introduced into RPS 1002 and/or chamber plasma region1015 may contain fluorine, e.g., NF₃. The process gas may also include acarrier gas such as helium, argon, nitrogen (N₂), etc. Plasma effluentsmay include ionized or neutral derivatives of the process gas and mayalso be referred to herein as a radical-fluorine precursor referring tothe atomic constituent of the process gas introduced.

FIG. 3C is a bottom view of a showerhead 1025 for use with a processingchamber in embodiments. Showerhead 1025 corresponds with the showerheadshown in FIG. 3A. Through-holes 1031, which show a view of first fluidchannels 1019, may have a plurality of shapes and configurations tocontrol and affect the flow of precursors through the showerhead 1025.Small holes 1027, which show a view of second fluid channels 1021, maybe distributed substantially evenly over the surface of the showerhead,even amongst the through-holes 1031, which may help to provide more evenmixing of the precursors as they exit the showerhead than otherconfigurations.

The chamber plasma region 1015 or a region in an RPS may be referred toas a remote plasma region. In embodiments, the radical-fluorineprecursor and the radical-oxygen precursor are created in the remoteplasma region and travel into the substrate processing region to combinewith the hydrogen-and-oxygen-containing precursor. In embodiments, thehydrogen-and-oxygen-containing precursor is excited only by theradical-fluorine precursor and the radical-oxygen precursor. Plasmapower may essentially be applied only to the remote plasma region inembodiments to ensure that the radical-fluorine precursor and theradical-oxygen precursor provide the dominant excitation.

Embodiments of the dry etch systems may be incorporated into largerfabrication systems for producing integrated circuit chips. FIG. 4 showsone such processing system (mainframe) 1101 of deposition, etching,baking, and curing chambers in embodiments. In the figure, a pair offront opening unified pods (load lock chambers 1102) supply substratesof a variety of sizes that are received by robotic arms 1104 and placedinto a low pressure holding area 1106 before being placed into one ofthe substrate processing chambers 1108 a-f. A second robotic arm 1110may be used to transport the substrate wafers from the holding area 1106to the substrate processing chambers 1108 a-f and back. Each substrateprocessing chamber 1108 a-f, can be outfitted to perform a number ofsubstrate processing operations including the dry etch processesdescribed herein in addition to cyclical layer deposition (CLD), atomiclayer deposition (ALD), chemical vapor deposition (CVD), physical vapordeposition (PVD), etch, pre-clean, degas, orientation, and othersubstrate processes.

Nitrogen trifluoride (or another fluorine-containing precursor) may beflowed into chamber plasma region 1020 at rates between about 1 sccm andabout 40 sccm, between about 3 sccm and about 25 sccm or between about 5sccm and about 10 sccm in embodiments. Oxygen (or anotheroxygen-containing precursor) may be flowed into chamber plasma region1020 at rates between about 10 sccm and about 400 sccm, between about 30sccm and about 250 sccm or between about 50 sccm and about 150 sccm inembodiments. Water vapor may be flowed into substrate processing region1070 at rates between about 5 sccm and about 100 sccm, between about 10sccm and about 50 sccm or between about 15 sccm and about 25 sccmaccording to embodiments. The flow rate ratio of the oxygen-containingprecursor to the fluorine-containing precursor may be greater than 4,greater than 6 or greater than 10 according to embodiments. The flowrate ratio of the oxygen-containing precursor to the fluorine-containingprecursor may be less than 40, less than 30 or less than 20 inembodiments. Upper limits may be combined with lower limits according toembodiments.

The showerhead may be referred to as a dual-channel showerhead as aresult of the two distinct pathways into the substrate processingregion. The fluorine-containing precursor and the oxygen-containingprecursor may be flowed through the through-holes in the dual-zoneshowerhead and the water vapor may pass through separate zones in thedual-zone showerhead. The separate zones may open into the substrateprocessing region but not into the remote plasma region as describedabove.

Combined flow rates of water vapor and plasma effluents into thesubstrate processing region may account for 0.05% to about 20% by volumeof the overall gas mixture; the remainder being carrier gases. Thefluorine-containing precursor and the oxygen-containing precursor flowedinto the remote plasma region but the plasma effluents has the samevolumetric flow ratio, in embodiments. In the case of thefluorine-containing precursor, a purge or carrier gas may be firstinitiated into the remote plasma region before those of thefluorine-containing gas and the oxygen-containing precursor to stabilizethe pressure within the remote plasma region.

As used herein “substrate” may be a support substrate with or withoutlayers formed thereon. The patterned substrate may be an insulator or asemiconductor of a variety of doping concentrations and profiles andmay, for example, be a semiconductor substrate of the type used in themanufacture of integrated circuits. Exposed “silicon oxide” of thepatterned substrate is predominantly SiO₂ but may include concentrationsof other elemental constituents such as, e.g., nitrogen, hydrogen andcarbon. In some embodiments, silicon oxide portions etched using themethods disclosed herein consist essentially of silicon and oxygen.Exposed “silicon nitride” of the patterned substrate is predominantlySi₃N₄ but may include concentrations of other elemental constituentssuch as, e.g., oxygen, hydrogen and carbon. In some embodiments, siliconnitride portions described herein consist essentially of silicon andnitrogen.

The terms “gap” and “trench” are used throughout with no implicationthat the etched geometry has a large horizontal aspect ratio. Viewedfrom above the surface, trenches may appear circular, oval, polygonal,rectangular, or a variety of other shapes. A trench may be in the shapeof a moat around an island of material. The term “via” is used to referto a low aspect ratio trench (as viewed from above) which may or may notbe filled with metal to form a vertical electrical connection. As usedherein, a conformal etch process refers to a generally uniform removalof material on a surface in the same shape as the surface, i.e., thesurface of the etched layer and the pre-etch surface are generallyparallel. A person having ordinary skill in the art will recognize thatthe etched interface likely cannot be 100% conformal and thus the term“generally” allows for acceptable tolerances.

The term “precursor” is used to refer to any process gas which takespart in a reaction to either remove material from or deposit materialonto a surface. “Plasma effluents” describe gas exiting from the chamberplasma region and entering the substrate processing region. Plasmaeffluents are in an “excited state” wherein at least some of the gasmolecules are in vibrationally-excited, dissociated and/or ionizedstates. A “radical precursor” is used to describe plasma effluents (agas in an excited state which is exiting a plasma) which participate ina reaction to either remove material from or deposit material on asurface. “Radical-fluorine precursors” describe radical precursors whichcontain fluorine but may contain other elemental constituents.“Radical-oxygen precursors” describe radical precursors which containoxygen but may contain other elemental constituents. The phrase “inertgas” refers to any gas which does not form chemical bonds when etchingor being incorporated into a film. Exemplary inert gases include noblegases but may include other gases so long as no chemical bonds areformed when (typically) trace amounts are trapped in a film.

Having disclosed several embodiments, it will be recognized by those ofskill in the art that various modifications, alternative constructions,and equivalents may be used without departing from the spirit of thedisclosed embodiments. Additionally, a number of well-known processesand elements have not been described in order to avoid unnecessarilyobscuring the present invention. Accordingly, the above descriptionshould not be taken as limiting the scope of the invention.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimits of that range is also specifically disclosed. Each smaller rangebetween any stated value or intervening value in a stated range and anyother stated or intervening value in that stated range is encompassed.The upper and lower limits of these smaller ranges may independently beincluded or excluded in the range, and each range where either, neitheror both limits are included in the smaller ranges is also encompassedwithin the invention, subject to any specifically excluded limit in thestated range. Where the stated range includes one or both of the limits,ranges excluding either or both of those included limits are alsoincluded.

As used herein and in the appended claims, the singular forms “a”, “an”,and “the” include plural referents unless the context clearly dictatesotherwise. Thus, for example, reference to “a process” includes aplurality of such processes and reference to “the dielectric material”includes reference to one or more dielectric materials and equivalentsthereof known to those skilled in the art, and so forth.

Also, the words “comprise,” “comprising,” “include,” “including,” and“includes” when used in this specification and in the following claimsare intended to specify the presence of stated features, integers,components, or steps, but they do not preclude the presence or additionof one or more other features, integers, components, steps, acts, orgroups.

The invention claimed is:
 1. A method of etching a patterned substrate,the method comprising: placing the patterned substrate in a substrateprocessing region of a substrate processing chamber, wherein thepatterned substrate comprises an exposed silicon oxide portion and anexposed silicon nitride portion; flowing a fluorine-containing precursorand an oxygen-containing precursor into a remote plasma region fluidlycoupled to the substrate processing region while forming a remote plasmain the remote plasma region to produce plasma effluents; flowing ahydrogen-and-oxygen-containing precursor into the substrate processingregion without first passing the hydrogen-and-oxygen-containingprecursor through the remote plasma region, wherein thehydrogen-and-oxygen-containing precursor comprises an O—H bond; andetching the exposed silicon oxide portion by flowing the plasmaeffluents into the substrate processing region, wherein the exposedsilicon oxide portion etches at a first etch rate and the exposedsilicon nitride portion etches at a second etch rate which is lower thanthe first etch rate.
 2. The method of claim 1 wherein the first etchrate exceeds the second etch rate by a factor of about 80 or more. 3.The method of claim 1 wherein the substrate processing region isplasma-free during the operation of etching the exposed silicon oxideportion.
 4. The method of claim 1 wherein thehydrogen-and-oxygen-containing precursor is not excited by any plasmaoutside the substrate processing region prior to entering the substrateprocessing region.
 5. The method of claim 1 wherein thefluorine-containing precursor comprises a precursor selected from thegroup consisting of atomic fluorine, diatomic fluorine, nitrogentrifluoride, carbon tetrafluoride, hydrogen fluoride and xenondifluoride.
 6. The method of claim 1 wherein the remote plasma region,the substrate processing region, the fluorine-containing precursor, theoxygen-containing precursor and the plasma effluents are essentiallydevoid of hydrogen during the operation of etching the exposed siliconoxide portion.
 7. The method of claim 1 wherein the fluorine-containingprecursor and the oxygen-containing precursor flow through through-holesin a dual-zone showerhead and the hydrogen-and-oxygen-containingprecursor passes through separate zones in the dual-zone showerhead,wherein the separate zones open into the substrate processing region butnot directly into the remote plasma region.
 8. The method of claim 1wherein the hydrogen-and-oxygen-containing precursor comprises one ofwater vapor or an alcohol.
 9. The method of claim 1 wherein theoxygen-containing precursor comprises one or more of O₂, O₃, N₂O, NO₂and N₂O₂.
 10. A method of etching a patterned substrate, the methodcomprising: placing the patterned substrate in a substrate processingregion of a substrate processing chamber, wherein the patternedsubstrate comprises an exposed silicon oxide portion and an exposedsilicon nitride portion; flowing nitrogen trifluoride and molecularoxygen into a remote plasma region fluidly coupled to the substrateprocessing region while forming a remote plasma in the remote plasmaregion to produce plasma effluents; combining the plasma effluents withwater vapor in the substrate processing region; and etching the exposedsilicon oxide portion with the combination of the plasma effluents andthe water vapor, wherein the exposed silicon oxide portion etches at afirst etch rate and the exposed silicon nitride portion etches at asecond etch rate which is lower than the first etch rate.
 11. The methodof claim 10 wherein the water vapor is flowed into the remote plasmaregion without first passing through the remote plasma region.
 12. Themethod of claim 10 wherein the first etch rate exceeds the second etchrate by a factor of about 120 or more.